Title : Characterization of human
glycogenin-2 , a self-glucosylating initiator of liver glycogen metabolism
Abstract :
- Glycogenin-2 is a recently described self-glucosylating protein potentially involved in the initiation of glycogen biosynthesis (Mu, J., Skurat, A. V., and Roach, P. J. (1997) J. Biol
- Chem
- 272, 27589-27597)
- In human liver extracts, most of the glycogenin-2 was only detectable after treatment with alpha-amylase
- Similarly, purifed high Mr glycogen was only detected after release by alpha-amylase treatment
- Based on analysis by polymerase chain reaction, the predominant isoform in liver was glycogenin-2beta
- Glycogenin-2 was found in Ewing's sarcoma RD-ES cells where, however, it was not associated with high Mr carbohydrate
- Both human liver and human RD-ES cell extracts also contained glycogenin-1
- Glycogenin-1 and glycogenin-2 interact with one another, based on in vitro interactions and co-immunoprecipitation from liver and cell extracts
- Mutation of Tyr-196 in glycogenin-2 to a Phe residue abolished the ability of glycogenin-2 to self-glucosylate but not to interact with glycogenin-1
- Stable overexpression of glycogenin-2alpha in Rat-1 fibroblast cells resulted in a 5-fold increase in the level of glycogen present in the low speed pellet but little change in the low speed supernatant
- This result is important since it indicates that the level of glycogenin-2 can determine glycogen accumulation and hence has the potential to control glycogen synthesis